This invention relates to an improved peristaltic pump in which fluid is pumped through a flexible hose by alternately squeezing and releasing progressive sections of the tubing.
Peristaltic pumps have been known for many years, and the prior art is replete with examples of various configurations of these pumps, which are also known variously as hose type or roller pumps. These pumps operate by holding a flexible elastic tube against a wall element in a pump chamber and progressively pinching or squeezing sections of the tube against the wall section with a cam or roller. Fluid ahead of the pinched tube section is displaced from the discharge end of the tube while the expansion of the tube in the wake of the pinched section creates a suction which draws more fluid into the intake end of the tube. The repeated pinching and releasing of the tubing creates stresses and wear such that eventually the tubing wears out. While the working lifetime of the flexible tubing can be extended by judicious selection of tubing materials, pump configuration, size and other factors, invariably the tube section in the pump chamber must be replaced. The lifetime of tubes ranges from several hours and up depending on the type of liquid being pumped and also the aforementioned factors of tubing material, pump configuration, etc. Various peristaltic pump configurations are shown in U.S. Pat. Nos. 4,496,295; 4,445,826; 2,651,2 64; 2,899,905; 2,958,294; and 4,380,236.
In many peristaltic pumps, the tubing section within the pump chamber is designed to remain stationary. It has been recognized that there is some tendency for the tube to creep relative to the pump chamber wall section due to the friction generated during movement of the cam or roller against the wall section. Some of the prior art patents have incorporated features to eliminate such tubing creep such as those described in U.S. Pat. No. 2,651,264. In other patents, the tubing is intentionally moved during the pumping action, such as in U.S. Pat. Nos. 4,380,236; 4,445,826; and 3,972,649. In the latter patent, an excess portion of tube is coiled around a rotating drum and fed through a pump chamber as the pumping action is applied. However, this method relies on an awkward and needlessly complex method of storing and feeding the tubes into the pump chamber.
Bearing in mind the deficiencies of the prior art, it is therefore an object of the present invention to provide a peristaltic pump which extends the working life of the tubing and requires less tubing changeover as a result of tube wear.
It is another object of the present invention to provide peristaltic pump in which fresh sections of tubing are continuingly feed into the pump chamber to replace worn sections.
It is a further object of the present invention to provide a tube feeding means for a peristaltic pump which operates in a simple yet efficient manner.
It is yet another object of the present invention to provide a peristaltic pump which is relatively simple, inexpensive and easy to manufacture.